Secrets of The Teen Brain Tom Sewell, summary of article in Time: May 10, 2004

Article based on research by Dr. Jay Giedd, National Inst. Of Mental Health Researched 1800 teens MRI snapshots every 2 years Research started 13 years ago and will continue until subjects are 25. Subjects also included twins: both identical and fraternal. Prior to MRI: Cadavers were primary source for brain research MRI shows that both gray and white matter undergo extensive structural changes well past puberty.

Previously Held Brain Information Most scientists thought brain was developed by 12 years of age. Piaget research in cognitive development, stages and ~12 years was start of formal operations. Adolescence behavior influenced by hormones and needed cognitive control to develop mature behavior.

Nature vs Nuture Brain preprogrammed by Genes Brain influenced by environment and external forces. Pruning in brain is guided by genetics and or Neural Darwinism. Neural Darwinism: use-it-or-lose-it principle.

Children Brain Development Age 6: Brain is 90-95% of adult size Age 6-12: Neurons grow brushier making more connections to other neurons = creating new paths Gray matter is thickening: Neurons and branching of dendrites Peak of thickening is ~11 for girls and ~12.5 for boys Gray matter: thins ~0.7% a year tapering off in early 20’s

Some New Facts Pruning takes place in waves to eliminate unneeded cells 1 st pruning is in final months before birth 2 nd wave of pruning starts in childhood with a final pruning in late teens This final pruning alters not the # of nerve cells by the # of connections (synapses)

Gray Matter Gray matter thickens: Neurons and branching of dendrites Peak of thickening is ~11 for girls and ~12.5 for boys Gray matter: thins ~0.7% a year tapering off in early 20’s Practicing piano: thickens neurons that control the fingers.

White Matter White matter is fatty myelin sheaths that encase axons and act like insulations. This helps speed nerve signals faster and more efficiently. Up to age 40 the myelin continues to thicken.

Synapses

Brain Regions Practicing piano: thickens neurons that control the fingers. Study of London cab drivers: found larger hippocampus: structure involved in memory.

Research Outcomes The Cerebellum which coordinates both physical and mental activities maybe responsive to experience. Development of brain generally proceeds from back to front. 1 st sensory functions, 2 nd coordination of those sensory functions, 3 rd prefrontal cortex.

Functions of Prefrontal Cortex Planning Setting priorities Organizing thoughts Suppressing impulses Weighing the consequences of one’s actions

Thoughts During the final stage of pruning the hormones are at their peak. Sex hormones are very active in limbic system of the brain. The parts of the brain responsible for sensation seeking are working overtime while the judgment section of the brain have not fully developed.

Web Resources Brain Basics: Nervous System: ml ml Synapses: Neurotransmitters: Limbic System: /limbic.asp /limbic.asp

Resource Park, Alice. “The Teen Brain." Time May :